Injection moulding is a technique used in the manufacturing of plastic products. Although it is a straight forward process there are many steps involved towards creating the finished product.
Injection moulding is a common manufacturing process used to create plastic products and materials. It involves inserting melted plastic into a mould cavity which has been designed into the required shape.
Many of the everyday items we see around us have been manufactured in this way – from the plastic components used in our electrical gadgets to the plastic coverings on our household appliances, and from the plastic interiors of our cars to the screw-top plastic lids on our drinks bottles – just about everywhere you look you can see a plastic object that would have been manufactured using an injection mould technique.
The injection moulding machine
A moulding machine, also known as an injection press, consists of two main parts: the injection unit and the clamping unit. Moulds can be fastened by injection machines in either a vertical or horizontal position, depending on the size or type of application required. A choice of cold or hot runner systems can also be selected for carrying the plastic into the mould cavities. Again, this will depend on the product being manufactured.
There are various types of moulding machines classified by the various driving systems they use, including: hydraulic, mechanical, electric or hybrid machines.
The injection mould process
Although the manufacturing of plastic products using an injection mould may seem quite simple at first (the plastic material is injected into a mould, left to cool, then removed when ready) there are however more complex steps involved in order for this seemingly simple process to occur. The six main steps are as follows:
- Clamping – the clamp unit consists of metal plates (or platen). The process begins with the mould being clamped together under pressure to accommodate the injection and cooling processes.
- Injection - the molten thermoplastic material, which has been melted by pellet form in the barrel of the machine, is injected under pressure into the mould through either a screw or ramming device.
- Dwelling - once the molten plastic is injected into the mould, more pressure is exerted to make sure all the mould’s cavities are filled, using hydraulic or mechanical pressure.
- Cooling - the plastic is left to cool and solidify within the mould.
- Opening - the movable platen is separated from the fixed platen to separate the mould.
- Ejection – ejection is completed by the use of rods, a plate or an air blast to remove the plastic component completely from the mould.
When looking for a company to assist you with your plastics manufacturing, make sure you understand the processes they use so you can get a better idea of how they operate and what you can expect from the finished product. Some manufacturers will allow you to take a tour of their facility and many will have videos and other useful production information posted on their website.
Don’t be afraid to ask your manufacturer about the injection moulding process – a few questions at the start will go a long way towards ensuring you get the best results.